THE World Health Organisation yesterday said it felt there was still a "window of opportunity" to try to wipe out the Sars virus.

THE World Health Organisation yesterday said it felt there was still a "window of opportunity" to try to wipe out the Sars virus. So far 4,439 people worldwide have been struck down by the mystery pneumonia-type virus and 263 have died.

The WHO accepted it was possible for Sars to become endemic, which would mean it would become a permanent threat, but it still believed there was a chance to wipe out Sars.

David Heymann, executive director of communicable diseases for the WHO, said, "We have a chance, we believe, to stop this disease if we all work together."

Dr Mike Ryan, co-ordinator of the Global Alert and Response Network for the WHO, said, "We have made a decision that there is a window of opportunity available to us and we will try to work with countries to take that opportunity.

"We believe we know enough about this disease and transmission that there is a chance to control the disease and deal with it in an effective way."

Dr Heymann said the greatest risk was if Sars reached countries, such as those in sub-Saharan Africa, where healthcare systems might not be able to cope and there was already a large population with HIV and or Aids.

"What is important is for all countries to participate and to help prevent it getting in a place where it would be very difficult to stop it," he said.

Of the 26 countries that had seen Sars cases, 23 had contained it well and it appeared Sars did not spread as easily as influenza.

"It hasn't spread like wildfire in the countries to which it has arrived," Dr Ryan said.

Dr John Hubley a lecturer in health promotion at Leeds Metropolitan University, said he felt Sars had the potential to wreak "absolute destruction."

"Though it's too early to say for sure what the impact of Sars will be, it is certainly far more contagious than Aids and the course of infection is much quicker," he said.

But Dr Ryan said, "At the beginning of the Aids epidemic we were dealing with a disease that was 100% fatal, with Sars that is not the case.

"The vast majority of people with it recover well."

Public health minister Hazel Blears insisted the Govern-ment's response to Sars had been "proportionate, responsible and effective."

She dismissed calls from the Tories for stricter controls on travellers saying, "In this situation we need to act responsibly we don't need to stoke up panic."

There have been six probable cases of the virus in the UK, but no deaths.

Thousands of Britons due to leave China will have to wait up to four days for a flight, it emerged yesterday. An exodus of travellers has left space on planes at a premium and many flights are fully booked.